This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. An understanding of the mechanism by which proteins fold and misfold is relevant to a number of human diseases and efforts to find therapeutics to treat them. To better understand the protein folding process and why proteins sometimes misfold, our efforts are aimed at understanding the fundamental principles guiding the acquisition of the native functional protein structure. Many proteins fold to the native state via intermediates, and small-angle scattering studies at BioCAT are instrumental in understanding their structural properties. In our studies this year at BioCAT, we have focused our efforts in two ways. First, to improve data collection efficiency, we have built an autosampler to allow higher-throughput automated data collection at the beamline. With the increased sample processing capability, we have performed an analysis of the equilibrium denaturation of two proteins (CheY and cytochrome c) that address fundamental questions on the role of topology and the role of the unfolded state ensemble in guiding folding. Our group has also studied the effect of Zn metal ions and an intrinsic disulfide cross-link has on the structure of Cu,Zn-superoxide dismutase (SOD), a protein implicated in Lou Gehrig's disease. Our results suggest that, in the absence of metals and the disulfide cross-link, disease causing mutants of SOD are structurally unfolded, and possibly more likely to aggregate, at physiological temperatures. With the structural studies made possible by BioCAT, we are also in the process of addressing the effect of disease causing mutations on the structure of the native state of SOD.